Selective signaling system



May 17, 1955 J. T. NEISWINTER SELECTIVE SIGNALING SYSTEM 2 Sheets-Shet 2 Filed April 12, 1951 x mN Uired SELECTIVE SEGNALENG SYSTEM James T. Neiswlnter, Garden City, N. Y. Application April 12, 1951, Serial No. 220,653

16 Claims. (Cl. 340164) This invention relates to signaling systems and particularly to code responsive selectors for remotely selecting a desired one out of a plurality of circuits for operation.

The object of the invention is to provide a reliably operating and economical selector for use in a great number of situations, one not confined to a special application but rather of universal or general adaptation.

The selector, in nature, is one which may be connected at the distant end of a communication channel and which will respond to simple on and oil timed signals. A large plurality of such selectors may be connected to such a channel, all responding to the on and off signals but only one completing an efiective circuit in accordance with the code of signals transmitted. The selector is reached over any appropriate type channel and has connected to its incoming terminals a line relay which may be adapted to any type of incoming signal so that a plurality of such selectors may be connected either in series or in parallel, the line relays of all selectors connected to the communication channel responding simultaneously. The most general and the simplest arrangement is one like a simple telegraph circuit, a complete loop containing a battery and a plurality of selectors in series wherein sig nals may be transmitted from any one of the selectors to operate all the others. Beyond the line relay within the circuit of the selector the wiring and arrangements will be standard.

In a preferred embodiment of the invention herein disclosed the selector is shown as one adapted for inclusion in a printing telegraph line and in which the line relay will respond to the line current therein. The selector will not be operated by the regular printing telegraph signals though the line relay will respond thereto, but will be operated by the code of timed on and oil signals produced at any one of the selector stations. The selector may be used for any desired purpose such as to connect a printing telegraph station into the line, to call in an attendant or to perform any given remotely controlled switching operation.

A feature of the invention is the use of a simple on and oil circuit condition broken up into the elements or" a timed code. Thus there are two circuit conditions used in regularly recurring alternative order each transmitted for a precisely timed interval. Examples of the type of circuit on which there are only two circuit conditions are a printing telegraph or simple control circuit where the two conditions are circuit closed and circuit open, a radio telegraph circuit where the two conditions are carrier on and carrier oil or a carrier of one frequency and then carrier of another frequency, or a telephone circuit where for signaling purposes the two conditions are ringing current or voice frequency current on and off. Given any normal and alternative condition, transmitting means operated by a key or other device may produce a code of these two conditions alternately applied and each precisely timed.

Each selector of the present invention includes a send- Z,?08,i44 Fatented May r7, 1955 ing part first in the form of a manually operated key which may be preset to a given code and then allowed to run down automatically or in the form of an automatic arrangement whereby a predetermined code is formed and transmitted automatically. The sending part of the selecting device thus creates timed pulses of one condition of the communication circuit interspersed by timed pulses of the other condition of the communication circuit. As an example, on a printing telegraph circuit in which the idle condition is marking, the device interrupts the marking condition to send the timed space pulses interspersed with timed mark pulses. In the preferred embodiment of the invention herein described three space pulses are transmitted interspersed with two mark pulses, the final space pulse being followed, of course, by the idle or normal mark condition of the telegraph circuit. In the particular application to be described, two lengths of space pulse are employed, namely .30 and .60 second, and two lengths of mark pulse, namely .12 and .42 second.

The receiving part of the selector is arranged so that in the idle condition but a single relay is operated, which is known as the line relay and which is included in the circuit of the incoming terminals of the device. If this selector is placed in series relation with the line then the normal line current will hold this line relay continuously operated until it is released by the response to a space signal. To operate the selector a space pulse of at least .20 second length must be received and since the longest space pulse occurring in the usual printing telegraph machine (60 words per minute) is .132 second, such printing telegraph signals will not operate the selector. The reception of the normal .30 or .60 second space pulse or" a signaling code will operate the first of a chain of relays in the selector and will present for possible operation the first of five selecting or tree relays. If the first space pulse is a long pulse (.60 second) this selecting or tree relay will be operated. The reception of the following .12 or .42 second mark pulse will operate the second of the chain of relays and will present for possible operation the second selecting or tree relay. If the mark pulse is a long one (.42 second in this case) this selecting or ree relay will be operated. The third pulse of the five which is the second space pulse will operate the third relay in the chain and will operate the third selecting or tree relay if the pulse is a long one. Pulses four and five operate the chain and selecting relays in a similar manner. After the final pulse which is a space the return of the line circuit to the normal marking condition operates the final relay of the chain which in turn applies battery through the tree circuit formed by the armatures and contacts of the selecting or tree relays to operate a final pair of relays out of a number of final pairs as determined by the arrangement of operated and non-operated tree relays.

The protection of the selector circuit from operation by printing telegraph signals comes from the arrangement whereby three relays of the chain require a space pulse of .20 second minimum to operate them, whereas the maximum space signal in a printing telegraph character at a speed of 60 words per minute, is .11 second, if the Blank character is not used, which is usually the case, or .132 second if the Blank is used. Thus printing telegraph signals cannot operate these particular chain relays. In addition, if the length of a space pulse is greater than .90 second or if a mark pulse is longer than .60 second, or if more than .90 second elapses before a proper length pulse is received all relays of the chain that are operated are released and the selector is restored to its idle condition Without having made a selection. Thus for the selector to be operated to completion by a series of accidental openings and closures of the line it would be necessary that each opening would be between .20 and .90 second long with each intervening mark between .020 and .60

second long, an occurrence which is thought to be extremely rare.

The peculiar characteristic about printing telegraph signals is that the space signals have a definite maximum length, never exceeded except by an interruption to the circuit, while the mark signals, in the case of hand sending, may be of almost any length since the pause between each letter while the operator looks for the next key, is always marking. Therefore, any system which 15 to be protected from false operation by printing telegraph signals must depend upon the maximum length spaces of the signals, and cannot depend upon any maximum length of mark. Therefore, while the space signals used in the selector system are longer than the maximum length space of printing telegraph signals, the mark signal might as well be shorter to speed the operation of the selector, since no protection is obtained from using long marks for signaling.

Another feature of the invention then may be stated as counting means for subjecting the code relays to the difference of the code elements. In the preferred embodiment of the invention herein disclosed this counting means is in the form of series of relays sequentially operated by the regularly recurring alternative line conditions each equal to or greater than a minimum predetermined time. The counting means may, however, take other forms such as a step-by-step switch, the stepping magnet of which is responsive to minimum length signals, or may be in the form of the familiar open chain or closed ring of electronic tubes.

Another feature of the invention is a timing means for measuring the length of an incoming signal and for thereupon, when such signal has endured for a minimum length of time, applying an operating current to the counting means. In the present invention this timing means is disclosed as an electronic circuit wherein the line relay operates a resistance and condenser circuit for firing an electronic tube which in turn operates a relay for applying an operating current to the counting means. Upon such an operation of the line relay a potential through a given resistance is applied to a trigger anode of an elec tronic tube but this is held to a low potential by a condenser of a given and predetermined capacity. As time elapses the potential applied to this condenser through the said resistance charges the condenser and as the condenser approaches full charge the potential of the trigger anode rises until a firing potential is attained. Such a resistance capacity and tube circuit is conventional and has been found in practice to be highly satisfactory and regular in its operation.

Another feature of the invention is a cascade of timing means. The first timing means will measure a minimum predetermined time interval whereupon a tube and then a relay will be operated. At this instant the second timing means will start to operate and this in turn will measure off another or additional minimum time interval and in like manner a third timing means will measure off a second additional minimum time interval. The first of these timing means measures the minimum interval required for an effective signal known as a short pulse. The second of these timing means measures the additional interval which added to the first interval measured constitutes the minimum length of time required as a long pulse and the third timing means measures a further additional time interval which summed with the two intervals previously measured constitutes a time interval recognized as a signal for release. Thus, after the closure of the line following one or two space pulses these three timing means will sequentially operate on the prolonged and continued mark signal constituting the normal condition of the line and will release all operated apparatus within the selector with the exception of the line relay. After a valid code containing three space pulses the operation of this third timing means is accelerated by a relay which signals the receipt of such a valid code.

Another feature of the invention is an answer back means. Where a selector of the present type is located remotely, it is desirable for the attendant who has attempted to operate such a selector to know whether or not the selector has operated. Therefore, an answer back means is provided which will operate only if the selector has performed as expected. This answer back signal is the transmission of an exact duplicate of the code used in its operation and is transmitted automatically when the selector has been operated. Though it is usual for the answer back signal to be an exact duplicate as stated, this may be changed for other purposes as when the answer back signal contains information selected and controlled by some condition at the site of the selector. Thus one relay of the pair of relays that is selected in the final operation of the selector may be employed to connect a printing telegraph machine to the line circuit, or to operate a hell or other signal or to perform some other function. The second relay is employed to cause the selector to send back to the line the identical combination of pulses that was received. The selector which originated the signals is arranged so that its receiving side ignores the outgoing signals but does receive the signals which are returned from the distant selector. The returned signals are selected in the standard manner for any incoming signals and caused to operate a relay or lamp signal to indicate to the operator that the proper distant selector has been reached and has been successfully operated. The lamp signal or relay will remain operated until the operator sends a disconnect signal and will thus be a constant indication to the operator of the stations he has caused to be connected to the circuit.

Another feature of the invention is the use of the code responsive relays for operating what is known as a tree circuit. Thus with five code relays it is possible to make a selection of one out of thirty-two circuits if the full complement of such circuits is provided for in the last of the tree relays. it is, however, not usual to provide for more than a small number of selection circuits in each selector so that the tree relays are not generally wired to their full capacity but only arranged for the specific codes to which they will respond. One typical case is where such a selector will respond to a single particular code and will be placed in service at such a point that it will. be only necessary for the operator thereat to transmit let us say five other different codes. Therefore, the tree relay conductors operated by the particular code to which the selector responds will be wired to the signal and answer back relays, the first of which is employed for performing the assigned function of the selector and the second of which is used for automatically returning the answer back code to the line. The other and remaining tree conductors will each be connected to a lamp sig nal herein disclosed as an electronic tube which may be triggered in the operation by the tree conductor and which will thereafter remain in operation until a disconnect signal is sent over the line. Such lamp signals may be .tsed to register answer back signals from distant selectors.

The drawings consist of two sheets having four figures, as follows:

Fig. l is a schematic circuit diagram of the selector;

Fig. 2 is a sequence chart showing the sequential option and release of the relays of the selector during the reception of a code and the transmission of the answer back code as an exact duplicate thereof;

Fig. 3 is a legend explaining the meaning of the various marks or devices used by way of explanation in the se quence chart of Fig. 2; and

4 is a labelled representation of a particular code it is used by way of explanation herein.

Operation of selector The detailed operation of the selector is as followsv incoming terminals of the device, here marked X,

L thence through armature 4 and back contact of the SEND relay to the other one of the incoming terminals. The relay L is therefore subject to the current flowing through the line which is normally of the order of 60 mils and which, therefore, maintains the relay L normally operated. The tube SP is a cold cathode tube which, when the potential difference between the cathode and the control grid exceeds about 70 volts, will ionize and set up a conducting path between the cathode and the anode. This tube has a permanent ground on the cathode and under the present condition of the selector, that is, with the line relay L operated, the control grid is grounded in a circuit from the armature and front contact of the line relay L, the armature 1 and back contact of the ACT relay to the control grid of the tube.

When a space signal is received, this is equivalent to an opening of the line circuit, so that the relay L becomes released. Therefore, the ground is removed from the control grid of the tube and a circuit is established from a plus potential of 120 volts through the armature 1 and the back contact of the SEND relay, thence in series through the resistance R3, the resistance R4 and the SP condenser and thence to ground. This starts the charging of the SP condenser so that it will become sufiiciently charged to raise the potential of the grid of the SP tube to its firing potential in the length of time indicated by the values noted alongside the resistances R3 and R4 respectively, that is .200 second. When the tube fires, a circuit is set up from battery through the resistance R5, the winding of the SP relay, the anode of the tube SP to the cathode thereof and thence to ground. The SP relay responds and locks in a circuit from ground via armature and back contact of the released line relay L, the back contact and armature 2 of the relay M, the armature 2 and front contact of the SP relay and the winding thereof. Since the ground thus applied to the winding of the SP relay is also applied to the anode of tube SP, this tube is extinguished. It should be particularly noted that, if the space pulse or the time during which the relay L is released is less than .200 second, the SP tube would have failed to fire and there would have been no operation of the SP relay.

Upon the operation of the SP relay a circuit is established from battery through the resistance R12 the back contact and armature 3 of the M relay, the armature 3 and front contact of the SP relay, the normal contacts of the S1 relay, and the winding of the S1 relay to ground. The S1 relay responds and locks in a circuit from battery through its operated contacts to the winding thereof to ground. As the S1 relay operates before the battery is removed from its normal contact, it should be noted that battery is extended through the operated contacts of the S1 relay to the winding of the M1 relay, but the M1 relay is short circuited at this time due to the battery applied through its normal contacts to the other terminal of its winding, so that it does not respond.

Upon the response of the SP relay, ground is extended through its armature 1 and front contact to the control grid of the SP tube, so that the SP condenser becomes short circuited. At the same time ground is removed from the terminal of the LP condenser so that this condenser starts to charge in a circuit from battery through the R6 resistance, the LP condenser to ground. A normal space pulse is .300 second and, since a time interval of .200 second has elapsed for the firing of the SP tube, the LP condenser cannot reach its full charge to cause the firing of the LP tube, since the timing circuit therefor is .200 second, as noted alongside the R6 resistance. Therefore, if this is a short pulse the line relay L willoperate on the following mark pulse and open theholding circuit of the SP relay which thereupon releases and terminates the charging of the LP condenser.

It should also be noted that upon the first operation of the SP relay a circuit-is established from ground, armature 4 and front contact of the SP relay,'the Wind- 6 ing of the ACT relay, the back contact and armature 3 ofthe CLR relay to battery. The ACT relay operates and locks through its own armature 2 and front contact and will remain in this condition until released by the operation of the CLR relay.

Now upon the operation of the line relay L on a mark pulse following a first space pulse the holding ground for the SP relay is removed and this relay releases. Upon its release, a circuit is established from battery through the winding of the M relay, the armature 3 and back contact of the SP relay, the front contact and armature it of the ACT relay, the front contact and armature of the line relay to ground to operate the M relay. It should be noted that the other side of the M relay is also connected through its armature 3 and back contact to a source of battery but a resistance R12 is inserted in this line, so that the direct ground placed on armature 3 becomes effective in operating the relay M while preventing a direct connection between battery and ground. Therefore, following the operation of the L relay the SP relay releases and the M relay operates. Thereupon, a timing interval is measured by a circuit extending from battery through the armature 1 and back contact of the SEND relay, the resistance R3, the armature 1 and front contact of the M relay to the upper terminal of the SP condenser and thence to ground on the cathode of the SP tube. It will be noted that the resistance R4 is short circuited in this circuit and hence the SP condenser will become charged to the firing voltage for tube SP in .020 second, relay SP will operate, and, as before, the LP condenser will start to charge. However, this normal short mark pulse is only .120 second long and since it takes .200 second for the LP condenser to charge, the LP tube will not be fired on a normal short mark pulse.

Therefore, on a mark pulse, after .020 second the SP relay operates and this closes a circuit from ground to armature and front contact of the line relay through the front contact and armature 3 of the M relay to armature 3 and front contact of the SP relay to normal contacts of the M1 relay through the winding of the M1 relay to operated contacts of the S1 relay to battery. The M1 relay responds and locks to the ground on its armature.

In this same manner the S2, M2 and the S3 relays are sequentially operated on the following space, mark and space pulses.

In case a first space pulse is received of a duration of .600 second, then the LP tube will fire and cause the operation of the LP relay, since the addition of the time intervals .200 second for the SP relay and .200 second for the LP relay, is less than the duration of the space pulse .600 second. Upon the operation of the LP relay a circuit is established from battery to armature 1 and front contact thereof and thence in a series circuit including the armature 3 and back contact in turn of each of the relays M3, S3, M2, S2 and M1 through the armature 3 and front contact of the S1 relay to the windin of the A relay to ground. The A relay thus responds to a long pulse if the first space pulse is of this nature. The HOLD relay which operates upon the first operation of the LP relay, in response to the first long pulse received, will be described in detail hereinafter, It will be noted that each of the A, B, C, D, and E relays constituting the rec relays will therefore respond only to long pulses when they are subjected by the stepping relays S1, M1 and so forth to the corresponding elements of the incoming code.

Following the third spacing signal which is the last element of the code, the line circuit will be closed so that upon operation of the M relaya circuit will be established from-battery from the S3 relay armature, through operated contacts of the S3 relay, armature 1 and back contact of the CLR relay, resistance R13, winding of the M3 relay, back contact and armature 2 of the SP relay, armature 2 and front contact of the M relay, front contact and armature of the L relay to ground, so that the M3 relay responds to the establishment of the normal line condition. Therefore, a circuit is established from battery through armature 2 and front con tact of the M3 re'iay through the armaturcs and contacts of the tree relays t0 the particular circuit which these relays in combination have established. In the drawing, by ay of xample, it will be assumed that the A, B, and C ree relays have been operated and that the D and E tree relays have not been operated. Therefore the circuit established by the M3 rclay will extend to the A31 relay and through the normal contacts of the F relay to the winding thereof, thereby operating both the PE. and AB; relays.

Since some one of the tree relays has operated, then the b" ery on the armature l. of the LP relay will have con extended through armature 3- and back contact of the M3 relay to normal contacts of the HOLD relay and the winding thereof to ground so that this relay will operate and lock to a battery, which it will be noted is lied as long as the ACT relay operated. The function of the l-lGL relay is to supply battery to the anodes of such tubes as the ST N and STN 2 tubes and the holding circuit of Fl. relay during the time relay M3 is operated.

It may also be noted that in case the tree relays establish a circuit to a tube such as the STN 2 tube, that upon the operation of the M3 relay battery will be extended to the control grid thereof so that this tube becomes immediately fired and will remain in this condition so long as the HOLD relay is operated. The glowing of this tube will operate as a signal lamp so that the operator at this particular selector station will know that the code just received is one which is expected. When on incoming signals from a distant point, the selector is used for the purpose of bringing in the particular station at which it is located, then a combination of an F1 and A81 (or F2 and ABE) relay is operated. When the operator at this station, however, uses his means thereat for selecting some other station, then upon the selection of that other station an answer back signal will be sent which is received by this station and in such case the tree relays will be operated to fire a tube such as the STN 2 tube to notify the operator that the station whose code he has transmitted has been properly selected and that it has in turn sent the proper answer back signal. In this manner an operator will know positively that a distant selector has been properly operated.

Clearing out circuit The CLR condenser has no battery connected to it during the idle condition of the selector since the battery shown connected through resistance R8 is applied only when the ACT relay is operated. Battery applied through resistance R5, winding of relay SP, armature 2 and back contact of relay LP, varistor V and back contact and armature F. of relay M3 to condenser CLR during the idle condition of the selector is reduced in voltage by the potentiometer effect of the back resistance of varistor V in series with resistances R8 and R14 so that the voltage applied to condenser CLR is below the firing voltage of tube CLR. During the idle condition of the selector tube CLR therefore will not fire.

When relay ACT is operated during the first space pulse of a signal, battery is connected directly to resistance R8 and condenser CLR starts to charge towards the firing voltage of the tube CLR. Before the condenser CLR voltage reaches the firing point for tube CLR, relay SP operates. With relay SP operated, ground from relay L armature is extended through the back contact thereof, back contact and armature 2 of the M relay, armature 2 and front contact of the SP relay, armature 2 and back contact of the LP relay, varistor V, and back contact and armature 1 of the M3 relay to the upper terminal of the CLR condenser, thus returning the condenser to ground Ill potential and preventing the firing of the CLR tube. If a space pulse is longer than .400 second, or a mark pulse is longer than .220 second, relay LP will operate, and by opening the circuit through its armature 2 and back contact, will remove the ground from condenser CLR, allowing this condenser to start to charge again. Normally on a space pulse .600 second long, .400 second will have been taken up before the operation of the LP relay. Now, upon the operation of the LP relay, the CLR condenser will start to charge. In .200 second after the LP relay operates, the space pulse will terminate and relays SP and LP will release. On the following mark pulse, relay SP will reopcrate in .020 second and apply a ground, over the path previously described, to condenser CLR, returning the condenser to ground potential. Since the condenser had been charging only a total of .220 second after relay LP operated, and .600 second is required to bring the condenser to the firing point for the tube CLR, the tube is not fired.

In the case of a space pulse following a long mark pulse, relay LP operates .220 second after the mark pulse begins, and condenser CLR starts charging. At .200 second later, or .420 second after the mark pulse began, it terminates and relays SP and LP release. Then, at .200 secend after the following space pulse begins, relay SP operates again to apply a ground to condenser CLR and return it to ground potential. Since the condenser had been charging only a total of .400 second after relay LP operated, tube CLR accordingly is not fired. In this manner the CLR relay is prevented from operating during the reception of normal length short or long ulses of a code. However, if either a space pulse or a mark pulse is prolonged for a duration of anything over .600 second after the LP relay has operated then the CLR tube will fire and the CLR relay will operate. The latter relay in moving its armature 3 will open the circuit for the ACT relay and this relay will release, thus removing the battery connections to many of the points in this circuit. This action normally happens after the normal line condition has been established after a fifth pulse of a code, whereupon the relays S1, M1, etc., and all the tree relays are released. Although the HOLD relay is also released by the release of the slow release ACT relay, the prior release of the M3 relay places battery from its armature 2 and back contact on the holding circuit of any signal tube, such as the STN 2 tube or, alternatively, the holding circuit of one of the F relays, such as the F1 relay, to hold this tube or relay operated during the clearing or the sclcctor. It may also be noted that the A83. relay operated in circuit with the F relay will have extended its operating circuit to and caused the operation of the SEND relay and will thereafter be locked in a circuit through the front contact and armature 3 of the SEND relay and first through the front contact and armature 3 of the CLR relay, and finally, after the ACT relay releases, through the back contact and armature 4 of the ACT relay. Thus, in the normal operation of one of these devices the circuits will be restored to normal with the exception of the F1, AB and SEND relays. The consequence of this circuit condition will be explained hereinafter under the description of the answer back arrangement.

Fzmcrion 0] hold relay Every combination of pulses except that of all short pulses must necessarily contain one or more long pulses. Therefore on any signal, except a code of all short pulses, relay HOLD will be operated as hereinbcfore described. At the conclusion of the signal, when relay M3 operates to operate the relays F1 and A81 or one of the station signals, such as STNZ. tube, the relay F1 or the tube will remain operated from battery supplied by the armature 2 and front contact of the HOLD relay. The operation of relay M3 connects battery from the normal lower contacts of the disconnect key through armature 2 and back contacts of the SEND relay, resistance R10, armature 1 and front contact of the M3 relay to the CLR condenser, which charges through resistance R10 in .020 second to fire the CLR tube and operate the CLR relay to clear the selector. The operation of relay CLR opens the circuit for the M3 relay, which releases immediately and which applies battery through its armature 2 and back contact to the holding circuit for the Fit relay or the station signal tube STNZ. Later, when the ACT relay has released and removed the holding battery from the armature 1 of the HOLD relay, the HOLD relay thus releases but the F1 relay or the station tube STNZ remains operated.

When it is desired to release relay F1 from a distant point, a disconnect signal consisting of all short pulses is sent so that no operation of the LP relay takes place and hence the HOLD relay is not operated. Therefore, when the M3 relay operates at the end of the signal the holding battery is removed from the relay F1 and this relay releases. A station tube STNR or STNZ which might have been in an operated condition to indicate the operated condition at a distant F relay, is extinguished.

by a disconnect signal.

Sending functions When it is desired to send a signal from the selector to call in some other station, the combination of long and short pulses desired in the signal is first preset on the code keys, shown at the right end of the drawing and connected to the armatures of the CODE relay. When the CODE relay is thereafter operated, these code keys will selectively connect battery to the A, B, C, D, and E points, each or which is connected to a back contact of the armature 1 of the Si, Mi, S2, M2 and S3 relays. If, for instance, it is desired to have the first space pulse short, then the code key A is left in its normally shown position so that battery will be connected to the point A when the CODE relay is operated. if it is desired that the first space pulse be long, then the code key A is operated so that battery is not connected to the point A. In similar manner short mark and space pulses may be preselected by leaving the corresponding code keys unoperated or, alternatively, long pulses may be preselected by operating such code keys and thereby removing battery from the corresponding points.

After the code keys have been set, the SEND key is momentarily operated. This key is shown in two parts, one part being at the extreme right of the drawing and shown in such a manner that when it is operated momentarily it will connect battery to the CODE relay. The other part, shown at the extreme left of the drawing, similarly will momentarily connect battery to the SEND relay. It will be understood that these two parts are operated by a common lever or button.

' When the SEND key is operated, therefore, both the CODE relay and the SEND relay will operate and both will lock in obvious circuits, the CODE relay through its armature 4 and front contact and the SEND relay through its front contact and armature 3 and thence through the back contact and armature 4 of the ACT relay or, alternatively, through the back contact and armature of the S3 relay to battery.

Through its armature 4 the SEND relay will open the line circuit and consequently release the line relay L. The release of this relay, as hereinbefore described, will start the charging of the SP condenser. it" this is to be a short pulse then battery through the code key A will be extended over armature 1 and the front contact of the CODE relay to point A associated with the S1 relay, back contact and armature 1 of the S1 relay, resistances R2, R3 and R4 in series to the SP condenser and thence to ground on the cathode of the SP tube. Therefore, the SP tubewill fire in .300 second and cause the operation of the SP relay. The operation of the SP relay, as hereinbefore described, causes the operation of the ACT relay.

If this first space signal, however, is to be a long pulse,

then no battery will be supplied to the back contact of armature 1 of the S1 relay and therefore the charging of the SP condenser is through the R1, R2, R3, and R4 condensers which will measure a time of .600 second. Upon the operation or" the ACT relay a circuit will be established for the S1 relay as hereinbefore described and tr is relay in operating will close the line circuit from armature 4 and front contact of the SEND relay, through armature 2 and front contact of the Si relay, armature 2 and back contact of the M1 relay, back contact and armature 2 of the S2 relay, armature 2 and back contact of the M2 relay, to the other side of the line. Therefore, relay L will respond to the closure of the line circuit and through its operation will release the SP relay. At this time the second pulse, a mark pulse, will be measured. A short mark pulse is .120 second long and a long mark pulse is .420 second long. if the code key B is not operated, then the battery will be placed on the back contact of armature ft of the M1 relay and this will be extended through the front contact and armature 1 of the S1 relay through the resistance R2, resistance R3, armature i. and front contact of the M relay, now operated, to the SP condenser so that this condenser becomes charged in .120 second to the potential necessary for causing the firing of the S? tube and consequently the operation of the S? relay. if, on the other hand, the B code key has been operated so that no battery connection is made to the point E, then the charging of the SP condenser will be from battery through resistances Rt, R2, R3, armature 1 and front contact of the M relay to the SP condenser causing the SP tube to fire in .420 second. it is believed that the further operation of the circuit will be obvious. The S1 relay, as described, will cause the closing of the line circuit, the M1 relay will open it, the S1- relay will again close it, the M2 relay will open it and finally the S3 relay will close it to establish the normal marking line condition.

Upon the operation of the S3 relay at the end of the last space pulse the last of the holding circuits for the SEND relay is opened and this relay releases. Upon the operation of the M3 relay the CLR relay will be operated, as hereinbefore described, thus clearing the selector. During the transmission of this signal the LP relay does not operate so therefore no one of the tree relays is operated and no one of the relays, such as F! or the station signals, such as STN2 will operate. If any one of the F1 relays or station signals has been operated prior to the sending of the code, such relay or relays will remain operated at the clearing out of the selector due to the fact that the HOLD relay had been operated as soon as the SEND relay has responded by battery from the closed contact at the disconnect key through armature 2 and front contact of the SEND relay, and through the back contact and armature 3 of relays 81, M1, S2, M2 and S3 and the normal contacts of the HOLD relay to its winding.

Answer back signal It appears from the above description that when a code is transmitted from a. given station the selector thereat is cleared at the end of such a transmitting operation and is, therefore, ready to receive the code now automatically transmitted by the answer back means at the distant selector which has just been operated. The reception of such an answer back signal will operate one of the station signals, such as the STNZ tube, to show to the operator that his transmitting operation has been successful.

At the distant selector the F1 and AB?! relays (or some other similar pair) have been operated, well as the SEND relay. Relay ABE is operated from battery armature 2 and front contact of the M3 relay through the tree circuit to the winding of the ABI relay and thence to ground. The ABl relay in operating extends thisbattery connection to the winding of the SEND relay which, in

operating, closes a circuit through its front contact and armature 3 to a number of points where a locking connection may be established. At the moment, since the ACT relay and the S3 relay are both operated, there is no battery available for locking the SEND relay and its operation depends upon the battery from the M3 relay. The operation of the M3 relay connects battery to the CLR condenser to start the last of the timing circuits. This battery is connected through the R9 and R10 rcsistances in series, armature 1 and front contact of the M3 relay to the upper terminal of the CLR condenser, so that this condenser charges in .040 second, fires the CLR tube and operates the CLR relay. The selector from which the signal has been sent and to which the answer back signal is about to be transmitted will clear with a timing of .020 second, as hereinbefore described, since its SEND relay will not be operated, and, therefore, the timing of its CLR relay will be controlled from battery through its disconnect key, its armature 2 and back contact of its SEND relay and thence through the resistance R10 and its CLR condenser. The purpose of the longer delay for a selector which has its SEND relay operated and is about to send an answer back signal is to make sure that the selector which is to receive this signal will definitely be cleared out before the signal arrives.

When the delay CLR operates, its armature 3 connects battery through its front contact to armature 3 of the SEND relay thereby establishing the holding circuit for the SEND relay and for the ABi relay in order to hold these relays operated during the subsequent removal of the battery presently being supplied by armature 2 of the M3 relay.

The operation of the CLR relay at its armature 3 opens the circuit for the ACT relay and this relay through its lower armature removes battery from many of the points in the circuit, such as the locking circuits of the tree relays, the locking circuit of the S1 relay, the operating circuit of the M relay and so forth. The battery on the winding of the SEND relay first supplied from the relay ACT through its armature 4 and back contact and later supplied "in parallel from the S3 relay is also connected through the A81 relay, thus holding this relay operated as long as the SEND relay is operated.

The operation of the CLR relay clears the selector as heretofore described and relay S3 which has been holding the line circuit closed through its armature 2 and front contact will be the last relay to release since it is the last in this chain of stepping relays. The release of relay S3 will then open the line circuit to release the relay L and start the action of sending out a code that will be similar to that previously described for the case where the action was started by momentarily operating the SEND key to operate the SEND relay.

In this particular case the A131 relay controls the selection of the code rather than the code keys connected through the code relay. Thus, in the typical example shown in Fig. 2 for operating the selector by a code consisting of first a short space signal, second a short mark signal, third a long space signal, fourth a long mark signal and fifth a short space signal, the ABI relay through its armatures and contacts connect battery to the points A, B, and E so that short space and mark signals will be form-ed in these elements of the code. The points C and D will be left unaffected so that long pulses will be formed. It is believed that the sending of this answer back signal will therefore be obvious without further description.

At the end of the fifth pulse the operation of the S3 relay will remove battery from the holding circuit for the SEND and the ABI. relays, thus allowing both these relays to release. The closing of the line circuit through the armature 2 and front contact of the S3 relay Will cause the operation of the M3 relay and the subsequent operation of the CLR relay to clear the selector.

Disconnect The operator at a station may clear out a glowing station signal by momentarily operating the disconnect key shown at the left end of the drawing. Through its upper springs this disconnect key will connect battery to the R2 resistance so that each element of the code sent through the operation of this key will be short. Through its lower spring the disconnect key applies battery to the SEND relay so that this relay becomes operated. The operator will hold his finger on this key momentarily so that a code of five short space and mark pulses is sent, which will entirely clear the selector. The total of five short pulses is 1.14 seconds, which means that the operator will merely have to firmly press the button for only this minimum period of time.

Sequence of operations Fig. 2 is used to illustrate the sequence of operations when an operator at a given station sends a code, such as that shown in Fig. 4, consisting of a short space, a short mark, a long space, a long mark and finally a short space. The sequence of operations is that in the selector responding to this code and will be explained here only in part since it is believed to be quite obvious from the foregoing description.

This sequence chart consists of two horizontal lines, the upper of which illustrates the actual line condition and the lower of which illustrates by a number of conventions explained in the legend of Fig. 3 how the various relays operate. Thus it appears that upon the beginning of the first space signal the relay L releases whereupon a time of .200 second is measured resulting in the operation of the SP relay and thereafter the operation of the ACT relay and the S1 relay. After a total interval of .300 second the L relay again operates since the line circuit closes at that time. Thereupon the SP relay releases and the M relay operates. Upon the release of the SP relay 2. time interval of .020 second is measured whereupon the SP relay again operates, this time causing the operation of the M1 relay. After a time interval of .120 second has elapsed through the reception of the first mark signal the line relay L releases, thereupon the M relay releases after a very short interval as measured by the slow releasing characteristic thereof. The SP relay releases since the M relay has been prevented from immediately establishing a holding circuit for the SP relay through its back contact and armature 2. A time interval of .200 second is now measured in the manner hereinbefore described, after which the SP relay again operates, this time causing the operation of the S2 relay. Since this space signal is .600 second in length an additional time interval of .200 second is measured by the LP tube and relay. Upon the termination of this second timing interval the LP relay operates thereby operating the C tree relay and the HOLD relay.

Upon the final clearing out after the operation of the CLR relay as described, the SP and ACT relays release, whereupon a circuit is established from ground, armature 4 and back contact of the SP relay, armature 3 and back contact of the ACT relay to shunt the CLR relay (the resistance R11 prevents a direct connection between battery and ground) to affect its release. Tube CLR is thus extinguished and the CLR relay releases. This relay is arranged for slow release to give tube CLR time to become extinguished.

Further detailed description of this sequence chart is believed to be unnecessary since the sequence of operations will be obvious.

What is claimed is:

1. In a signaling system employing intelligence signals having elements whose periods of duration do not exceed a predetermined maximum time duration a selector circuit comprising a plurality of relays connected and arranged to respond sequentially to a series of two recurring alternative circuit conditions each equal to or greater than a predetermined maximum time duration of said intelligence signal elements, a companion relay for each of said first relays, each said companion relay being responsive to one of said circuit conditions only when said circuit condition persists for a time greater than said predetermined amount, a first timing means for measuring the said predetermined duration, circuit means controlled thereby for operating said first relays, a second timing means connected in cascade relation to said first timing means for measuring a predetermined minimum time following the measurement of said predetermined duration by said first timing means, circuit means controlled by said second timing means for operating said companion relays and selection circuits controlled in combination by said companion relays.

2. A selector comprising a plurality of relays connected and arranged to respond sequentially to a series of two recurring alternative circuit conditions each equal to or greater than a predetermined time duration, a companion relay for each of said first relays, each said companion relay being responsive to one of said circuit conditions only when said circuit condition persists for a time greater than said predetermined amount, a release relay responsive to any one of said circuit conditions exceeding by a predetermined amount the time duration required for the operation of said companion relays, a plurality of timing devices each for measuring a predetermined time interval, mutually controlled means for operating said timing devices in sequence to measure varying time intervals from a predetermined minimum time to an aggregate predetermined minimum consisting of the sum of the intervals measured by said devices, circuit means controlled by said timing devices for operating said relays and selection circuits controlled in combination by said companion relays.

3. A selector comprising a stepping means for counting oil? the elements of a code consisting of a series of two regularly recurring .alternative circuit conditions each equal to or greater than a predetermined time interval, a relay for each code element connected in circuit by said stepping means for response to its assigned code element and responsive thereto only when said code element is greater than said predetermined time by an additional predetermined time interval, selection circuits controlled by said relays in combination and answer back means for transmitting an exact duplicate code of said two alternative circuit conditions, said answer back means being controlled by said stepping means.

4. A selector control apparatus for use with a signaling channel over which intelligence signals may be transmitted, said intelligence signals comprising timed periods of alternation between a relatively normal and a relatively abnormal signaling channel condition, said abnormal periods having a predetermined maximum duration, said selector control apparatus comprising in combination; counting means including a plurality of relays in cascade relation to one another coupled to said channel and arranged to respond sequentially to other timed periods of alternation between said normal and abnormal channel conditions so related as to form a coded group whose timed periods define elements equal in number to said relays; means connected with said counting means to prevent the response thereof to timed periods less than predetermined maximums for said intelligence signals; a separate relay means connected with the respective members of said plurality of relays; means coupled with said channel and plurality of relays for conditionally actuating each of said separate relays only if the circuit condition to which its corresponding counting means relay responds persists for a predetermined minimum timed duration in excess of said intelligence signal maximum duration value; and selective circuit switching means coupled with said separate relays for conditionally actuating predetermined circuits in accordance with predetermined combinations of actuated separate relays only upon the receipt of the final timed period of a given coded group.

5. A selector control apparatus according to claim 4 wherein there is additionally provided means connected with said signaling channel for conditionally producing normal and abnormal circuit conditions over said signaling channel; and means coupled with said counting means and said last named means for conditionally utilizing said counting means to also control the sending of code groups over said channel whose timed periods of alternate normal and abnormal channel conditions define elements equal in number to said plurality of counting means relays.

6. A selector control apparatus according to claim 5 wherein means are additionally provided coupled between said predetermined circuits to be activated and said code group sending means to initiate the sending of discreet and respectively difierent code groups immediately upon actuation of predetermined circuits.

7. A selector control apparatus according to claim 4 wherein there is additionally provided timing means coupled with said channel and said relays for clearing said relays in response to said normal and abnormal circuit conditions of a timed duration in excess of a predetermined maximum.

8. A selector control apparatus for use with a signaling channel over which teletypewriter character identifying signals are to be sent, said identifying signals comprising mark and space circuit conditions, said space circuit conditions having a maximum period of duration, said selector control apparatus comprising in combination: counting means including a plurality of relays in cascade relation to one another coupled to said channel and arranged to respond sequentially to received mark and space circuit conditions other than said teletypewriter identifying signals and so related as to form function code groups whose timed mark and space periods define elements equal in number to said relays and Whose timed mark and space periods are of a duration greater than said teletypewriter character identifying signals; means connected with said cascade relays to prevent response thereof to mark and space circuit conditions of timed durations equal to or less than said teletypewriter character identifying mark and space circuit conditions; a separate relay means connected with each of the members of said plurality of relays; timing means coupled with said channel and said plurality of relays for conditionally actuating each of said separate relays only if the circuit condition to which its corresponding cascade relay responds persists for at least a predetermined time in excess of said teletypewriter signal mark and space conditions; and selective circuit switching means coupled with said separate relays for conditionally activating predetermined function circuits in accordance with predetermined combinations of actuated separaterelays only upon the receipt of the final space period of the function code group.

9. A selector circuit terminal apparatus comprising in combination: a first controllable timing means for conditionally delivering an output signal only upon the actuation of said timing means for a period in excess of a given minimum, channel condition sensing means adapted for connection to a signaling channel and said timing means for conditionally initiating and terminating operation of said timing means in accordance with code signals over said channel, said code signals comprising groups of successive timed periods of alternation between normal and abnormal channel conditions, counting means comprising a plurality of cascade relays equal in number to the timed periods comprising said code signals, a connection from said counting means to said first timing means for actuating successive counting relays in respective response to said code signal timed periods of normal and abnormal channel conditions only when said periods exceed said first timing means minimum, a second timing means connected in cascade with said first timing means and actuated by said first timing means output signal to deliver another output signal only if said second timing means remains actuated for a period in excess of a given minimum, signal coincidence switching means connected with said second timing means and each relay of said counting means for conditionally effecting predetermined switching in response to constant actua ion of a given counting means relay and delivery of a second timing means output signal and a third tin 'ng means connected in cascade with said second timing means and having an output circuit coupled with said counting means, said other timing means and said switching means for clearing the selector circuit terminal apparatus in response to periods of normal or abnormal signaling channel conditions in excess of predetermined minimum duration.

10. A selector circuit terminal apparatus according to claim 9 wherein there is additionally provided sending means connected with said signaling channel for producing normal and abnormal signaling channel conditions, means coupled with said sending means and responsive to said counting means to actuate said sending means, means for varying the timing of said first controllable timing means for each timed period of counting means relay operation and means for initiating operation of said first timing means apart from the appearance on said signaling channel of a code signal.

11. A selector circuit terminal apparatus according to claim 9 wherein there is additionally provided means coupled with said channel condition sensing means and said first timing means for response to the output signal thereof to alter the timing of said first timing means for alternate periods of timing thereby.

12. A selector circuit terminal apparatus according to claim 10 wherein there additionally is provided means connected with said sending means and said first timing means for altering the timing characteristic thereof in response to operation of said sending means.

13. In a selector circuit terminal apparatus adapted for connection to a signal channel for conditionally defining a code signal comprising a predetermined number of grouped alterations between a first and a second signal channel signaling conditions, said apparatus comprising the combination of: a timing means for producing actuation signals of measured timed duration, a plurality of cascaded relays connected in counting relation to one another, and equal in number to the number of grouped alternations comprising a code signal, a set of sending contacts and a set of timing contacts associated with each relay, means connected with said sending contacts and said signal channel for producing in said channel successive periods of said first and second signal channel conditions, means connected between said timing contacts and said timing means for conditionally altering in response to actuation of members of said cascaded relays the measured timed duration of actuation signals produced by said timing means.

14. A selector timing system for discriminating in time between successive elements of a code group sent over a signal channel, successive code group elements being defined by alternation between a first and a second signal channel condition, said first condition representing the signal channel condition during rest, said timing system comprising in combination, a channel repeating means connected with said channel for responding to first and second signal channel conditions thereon, a first gas tube time constant charging circuit adapted to fire after a predetermined minimum time following actuation thereof, means connected with said repeating means and said first charging circuit for disabling said charging circuit during rest conditions on said line and inaugurating charging of said charging circuit upon the occurrence of said second signal channel condition, a first relay means coupled with said charging circuit for actuation upon firing thereof, a second gas tube time constant charging circuit coupled with said first charging circuit, means coupled with said first relay means and said second charging circuit for disabling said second charging circuit during the unfired condition of said first charging circuit but inaugurating charging of said first charging circuit, a second relay means coupled with said second charging circuit for actuation upon firing thereof, a third relay means coupled with said first relay means for actuation upon actuation of said first relay means, and a fourth relay coupled for actuation with said second and third relays upon the condition of said second relay actuation during the actuation of said third relay means, and utilization selection means coupled with said fourth relay for control thereby.

15. Apparatus according to claim 14 wherein means are additionally provided coupled with said first relay means for altering the time constant of said first charging circuit upon firing thereof.

16. In an electrical sensing circuit the combination of: a time constant timing circuit conditionally productive of actuating pulses, a plurality of chain connected relays connected with said timing circuit, each relay having a self locking means and circuit switching means whereby to energize successive relays in response to successive timing pulses, and means connected with each of said relays and said timing circuit for conditionally varying the timing thereof in response to actuation of successive relays, and means coupled with said relays for developing a utilization signal depicting the timing of successive relay actuation.

References Cited in the file of this patent UNITED STATES PATENTS 1,867,209 Chauveau July 12, 1932 1,970,455 Humphries Aug. 14, 1934 2,094,733 Byrnes Oct. 5, 1937 2,176,040 Brixner Oct. 10, 1939 2,334,574 Neistvinter Nov. 16, 1943 2,406,834 Hartley et al. Sept. 3, 1946 2,419,799 Swan Apr. 29, 1947 2,446,943 McGoffin Aug. 10, 1948 2,485,551 Angel Oct. 25, 1949 2,534,746 Wells Dec. 19, 1950 

